A headrest for a motor vehicle basically serves to block excessive rearward travel of a passenger or driver of a motor vehicle in an accident. In certain crash situations, however, additional horizontal forces act upon the head of the seat occupant. U-shaped or concave headrests are known, but are not considered comfortable and have the problem of being difficult to adjust for the user.
The headrest according to EP 0 578 452 deforms to cup the head of the wearer, but does not really provide any significant resistance to side-to-side or vertical displacement of the user's head, since the peripheral regions of the cushion are undeformed and quite soft. The head-engaging part of the headrest comprises a sealed outer, flexible sack made of plastic, as well as an inner flexible sack made of plastic. An inner space of the outer sack is only partially filled with air and therefore has a slack shape. An inner space of the inner sack is filled with flexible polyester material. The inner space is connected with the inner space of the outer air sack by side holes of the inner air sack. As long as the inner air sack is not bearing a load, the polyester material takes on a certain shape and thereby stores a certain amount of air.
In the event of an impact of a motor vehicle, the head of the occupant is thrown against the head-engaging front face and first the outer, slack air sack and then the inner air sack in the bearing portion are deformed. As a result of the compression, air flows out of the inner air sack through the side holes into the outer air sack, and the sides of the outer air sack bulge out. The side portions of the outer air sack form, however, no stable side guide for the head of the occupant is because as soon as a force is exerted upon the side portion, the air can flow out of the side area of the outer sack, for example, into the middle portion of the inner space, as a result of which the side area slacks and no longer provides any face. Beyond that, the optical design possibility of this headrest is low, because of the slack outer sack.
A different headrest is described in DE 101 36 523. The head-engaging component of the headrest can be adjusted between two positions. In a first operating position, the head-engaging component offers support to the head of the occupant that is in the upright position, for example, in the event of an impact. In a second reclining position, the head-engaging component takes on a shape in which it supports the head of the occupant in a sleeping and reclining position. The head-engaging component of this headrest comprises a cushion component with an inner space that is surrounded by an air and water-tight flexible casing, by means of which the inner space can be hermetically sealed. The hermetically sealed inner space can be opened by a valve, so the volume of the inner space can be changed. After the change of the volume, the inner space is closed again by the valve, so that the volume of the inner space remains constant. An elastically deformable foam element is located in the inner space, which completely fills the inner space.
Adjustment into the reclining position is performed by compressing the foam element when the valve is open. Air can escape from the inner space. The head-engaging front face takes on a concave shape, and side support portions are formed. For forming the side support portions, the head-engaging component has insertion components consisting of hard foam, that are formed side to the inner space. Subsequently, the valve is closed so that the head-engaging front face remains in the selected position. For an adjustment into the operating position, the valve is opened. The elastic reset force loads the foam element into its original position when the valve is open, as a result of which the head-engaging component moves into the operating position when air streams into the inner space. If the headrest is in the operating position, it does not form a thrust bearing for forces that are directed horizontal to the seat direction.
In U.S. Pat. No. 3,680,912 another headrest is shown having a liquid-filled bladder than can deform and drain to cushion the user's head. This structure is complex and still does not provide solid side-to-side and vertical barrier to movement of the user's head in the event of a collision.